We recently went on a 3,000 mile loop around the Great Lakes and were camping off the bikes. The other guys were running around campgrounds at night plugging stuff in to available sockets and then fretting over their security while out of sight. With the electric tank bag approach, my iPhone and my cameras were all completely charged when I turned in at night and got plugged back in underway first thing in the morning.
The only thing that was a remotely fussy item was the charge on my Sena BT equipped hat. The good thing is, even with an open bike2bike intercom channel open all dang day, the battery never failed even on 12+ hour riding days. So, I'd hang my Sena on their chargers at the camp ground or, the Sena has the feature that it will charge while it is in use. All it took was a USB cable going from the Sena on my hat into my tank bag for a few hours and it was fully charged again.
My K1600GT has a CANBUS powerlet port in the fairing and I plug the tank bag in there with a right angle cable. It's reasonably weather resistant (we rode in some torrential rain and never had a problem) and it's easy to disconnect and take the tank bag and all my electronic goodies into the restaurant with me.